Today, almost all mobile phones are equipped with a clock, including PDA's, which also maintain calendaring, and, in some instances, EMail and Browser functions. In some digital cellular/PCS systems, such as the IS-95/2000 CDMA system, the clock in a phone is synchronized to the precise local time (Coordinated Universal Time (UTC)+time zone) given by the base station to which the phone is currently communicating with. Once synchronized, the mobile station maintains the clock until the phone is turned off. As a result, users of such phones do not have to adjust the in-phone clocks while they are in a digital service coverage area.
However, if the mobile phone is powered up outside of a digital service coverage area, the mobile station will lose the current time, unless it is equipped with a battery-back-up real-time clock hardware (RTC). The RTC maintains the clock while the mobile phone is turned off, but requires extra physical space within the phone and increases the manufacturing costs. For a mobile phone without an RTC, applications that rely on the clock do not function when the current time is lost. For example, in such a case the “alarm clock” feature will miss the time at which it is supposed to give a visual/audible alert to the user.
In addition, because a RTC is normally driven by a low-cost crystal oscillator with only marginal accuracy, the mobile phone may not have a sufficiently accurate clock even if it is equipped with an RTC.
Some mobile phones provide the capability for users to set the current time manually. However, a user may not be aware of the need to set manual time, or may forget to set time manually, and thereby not receive important clock-dependent information, or receive the information at an inappropriate time.
The United States Federal Communications Commission (FCC) mandates that mobile phone manufacturers integrate a position determining mechanism in their products, in order to locate emergency callers. Today, the technology of Global Positioning System (GPS) is widely used for such position determination. Thus, it is expected that majority of newly manufactured mobile phones will be shipped with a GPS receiver. In such a phone, the GPS receiver is typically activated while synchronized to a base station that provides digital cellular/PCS services.
U.S. Pat. No. 6,433,734, of Krasner, granted Aug. 13, 2002, for Method and apparatus for determining time for GPS receivers, describes a method of using time information obtained from cellular network to calibrate a GPS receiver.
U.S. Pat. No. 6,430,415, of Agashe et al., granted Aug. 6, 2002, for Method and apparatus for locating GPS equipped wireless devices operating in analog mode, describes a method for locating a mobile device that may not have a sense of network time.
U.S. Pat. No. 6,427,120, of Garin et al., granted Jul. 30, 2002, for Information transfer in a multi-mode global positioning system used with wireless networks, describes methods for a GPS receiver to switch operation modes, such as between a stand alone mode and a network-aided mode.
U.S. Pat. No. 6,411,811, of Kingdon et al., granted Jun. 25, 2002, for System and method for provisioning assistance global positioning system information to a mobile station, describes a method for a cellular network to determine a mobile station's location, but does not provide any mechanism for managing the mobile station's clock.
U.S. Pat. No. 6,389,291, of Pande et al., granted May 14, 2002, for Multi-mode global positioning system for use with wireless networks, describes a method for a GPS receiver to switch operation modes, such as between a stand alone mode and a network-aided mode, but does not provide a mechanism for setting receiver time while outside of cellular coverage.
U.S. Pat. No. 6,252,543, of Camp, granted Jun. 26, 2001, for Location system combining ranging measurements from GPS and cellular networks, describes a method of combining information from both GPS satellites and cellular base stations to improve location determination.
U.S. Pat. No. 6,150,980, of Krasner, granted Nov. 21, 2000, for Method and apparatus for determining time for GPS receivers, describes a method of using time information obtained from cellular network for a GPS receiver, but does not teach or suggest use of a GPS signal to set an internal clock in the mobile communication device.
U.S. Pat. No. 5,945,944, of Krasner, granted Aug. 31, 1999, for Method and apparatus for determining time for GPS receivers, describes a method of using time information obtained from cellular network for a GPS receiver.
My U.S. Patent Publication No. 2002/0098857 A1, published Jul. 25, 2002, for Clock for mobile phones, describes a method of managing time zone changes for mobile devices.
United States Publication No. 2001/0050633 A1, of Thomas, published Dec. 13, 2001, for Land based method and apparatus for providing precise time and position (terrestrial alternative of the global positioning system—GPS), describes a method for providing precise time information from the GPS network to mobile GPS receiving unit.